The present invention aims in particular to a coupling for an electric shaver of the type having at least one cutter unit with a foil type upper cutter and a non-foil type lower cutter which perform a reciprocating relative movement with respect to each other when in use. In electric shavers of this type there is a general desire for adapting the cutter unit to the contour of the skin to be shaved. This is achieved by allowing a relative movement of the cutter unit with respect to the main housing or a handle of the electric shaver. A constraint in the adaption to the contour of the skin to be shaved is that the oscillating movement of a drive unit is transferred via the transmitter to a cutter element, typically the non-foil type lower cutter element.
Without such a coupling between the transmitter and the cutter element these two component parts may perform six types of relative movements corresponding to the six degrees of freedom of a rigid body, namely a translation parallel to a vertical axis (up and down), a translation parallel to a horizontal axis (left and right), a translation parallel to a further horizontal axis (forward and backward), a rotation about a vertical axis (gyration), a rotation about the horizontal axis (swiveling) and a rotation about the further horizontal axis (tilting). The further horizontal axis is defined as being perpendicular to the vertical axis and perpendicular to the horizontal axis and is referred to in the following as the tilting axis. The relative movement of the lower cutter element with respect to the upper cutter element is referred to in the following as being the movement parallel to the horizontal axis.
Regarding the orientation of the axes of an electric shaver, it is assumed in the following that the shaver is held in an upright position with a body or handle of the shaver facing downwards and a cutter unit facing upwards. With this orientation of the shaver, the vertical axis extends along the body or handle in a vertical direction, while the tilting axis and the swiveling axis extend horizontally. Although all three axes do not necessarily cross in on point they are oriented perpendicular relative to each. The term horizontal swivel axis as applied herein below includes also an axis which is parallel to that. Notwithstanding this definition of the axes, the shaver may be held and applied in any desired orientation during use.
FR 1 391 957 A describes a coupling between a driver which performs an eccentric rotational movement and a cutting element which performs a combined rotational and translational movement. The driver comprises a hemispherical tip which is smaller than a hemispherical shell of the cutting element.
EP 1 161 325 B1 suggests an electric shaver with oscillating cutting knifes which move relative to a shearing blade. A shearing head carrying the shearing blade is driven by a drive unit to perform a gyration or tilting movement.
U.S. Pat. No. 5,715,601 discloses an electric shaver with an inner cutter driven to reciprocate relative to an outer cutter. The outer cutter is floatingly supported in a holder so as to be capable of tilting and depressing together with the inner cutter against the bias of a spring. The inner cutter is formed with a joint and catch for detachable connection to a drive unit and its pin.
EP 1 005 404 B1 discloses an electric shaver with a with a housing in which an electric drive mechanism is provided having a drive element for the transmission of a driving motion to at least one reciprocating cutting element. A shaving head is mounted on two support arms of a supporting frame for pivotal movement about the horizontal axis within a shaving head frame. The shaving head is formed by at least two cooperating cutting elements disposed in the shaving head frame.
Further examples of shaver heads pivotable about the horizontal (swiveling) axis are described in DE 10 2006 010 323 A1. One of these examples uses a con-rod mounted to an eccentric portion of a drive shaft for driving an oscillatory bridge which in turn transmits the reciprocating translational movement to a lower cutter element. The con-rod comprises a pin engaging a slot in the oscillatory bridge which slot extends perpendicular to the horizontal (swiveling) axis. An alternative example uses pin-shaped oscillators which are each coupled via a joint pushrod to an oscillatory plate which in turn transmits the reciprocating translational movement to a lower cutter element. Both examples allow swiveling of the shaver head with respect to the shaver housing while transmitting a movement to the lower cutter element(s).
Further, EP 1 661 672 A1 describes a shaver coupling for transmitting a driving movement from an oscillating transmitter extending along a vertical axis to a cutter element moving along a horizontal axis perpendicular to the vertical axis. The coupling comprises the transmitter, the cutter element and a coupling part having a seat for receiving the transmitter. The cutter element is constrained to the transmitter in a direction parallel to the horizontal axis while having a degree of freedom in at least two rotational directions for performing a swing movement and a tilting movement, respectively, and in a direction parallel to the vertical axis.
It is accordingly an object of the present invention to propose a coupling of the type mentioned above which improves the ability of adaption to the contour of the skin to be shaved while transmitting forces from a driven part of an electric shaver to a cutter element.